(a) Technical Field
The present invention relates to a hold-back device for a carriage, more particularly, to a device for restricting movement of a platform carriage that is used to convey vehicles and workers in an assembly line of a factory for assembling complete vehicles.
(b) Description of the Related Art
In general, in a vehicle production line, a plurality of rows of assembly lines are arranged in parallel in the production line for assembling a vehicle, and various components are assembled into a vehicle body while the vehicle body is conveyed along the plurality of assembly lines in a state in which the vehicle body is placed on a carriage.
In the production line, various components are assembled into the vehicle while the carriage on which the vehicle is placed and a vacant carriage on which no vehicle is placed are moved from one line to another line.
Typically, separate rails are installed on a floor between the respective lines, and the carriage is conveyed to the next line across a passage between the respective lines.
For example, a hold back system, which is adopted in a factory for assembling complete vehicles, refers to equipment for preventing an increase in interval between carriages that are used to convey vehicles and workers in trim/final/chassis marriage lines in the factory for assembling the complete vehicles.
In the hold-back system, when rollers are attached to a motor and both surfaces of the carriage are pushed at a driving unit in each line (at one starting position in each line), thirty to forty carriages are simultaneously moved along a free roller track.
When the line is stopped (break time/meal time/closing time/non-operation) during the movement of the carriages, the carriages, which are being moved forward, are pushed by inertia instead of being stopped, and as a result, a gap occurs between the carriages.
In a case in which the gap between the carriages is large, a worker's foot may fall into the gap between the carriages, thus causing an accident, and the carriage cannot be stopped at a position that requires automation and synchronization, such that a non-operation occurs when the carriages are restarted.
In order to prevent the above problem, rollers are attached to an electric motor at a driven unit (at the end of an assembly process) in each line, and the rollers are rotated reversely to push the carriages reversely, thereby preventing an increase in the gap between the carriages.
The hold-back device for a carriage in the related art includes an electric torque motor, a speed reducer, and a driving roller which is mounted on a speed reducer shaft and comes into contact with the carriage, and when the carriage is moved, the driving roller rotates by an operation of the electric torque motor in a reverse direction to a direction in which the carriage is moved, thereby pushing the carriages in the reverse direction while providing friction interference to the carriages.
Further, when the motor is stopped when the line is stopped, the rotation of the driving roller is stopped, thereby stopping the carriage.
However, because the carriage moves in a forward direction and the driving roller rotates in the reverse direction, there is a problem in that a large amount of load is applied to the electric torque motor.
The electric torque motor is manufactured to endure high-temperature heat (80° C. to 125° C.), but as the high-temperature heat is continuously generated, an accident and a non-operation often occur due to frequent failure of the motor.
The above information disclosed in this Background section is only for enhancement of understanding the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.